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HENRY LIVINGSTONE SULMAN AND FRANK LlTl-IERLAND TEED, OF LONDON, ENGLAND.

EXTRACTION OF PRECIOUS METALS FROM THEIR ORES.

SPECIFICATION forming part of Letters Patent No. 610,616, dated September 13, 1898.

Application filedllovemher 6, 1894. Serial No. 528,081. (No specimens) Patented in England September 21,1894,No.18,003, September 24, 1894,No. 18,146, and October 1, 1894, No. 18,592, and in Germany November 13,1894,No. 83,292.

To all whom it may concern.-

Be it known that we, HENRY Livmosronn SULMAN and FRANK LITHERLAND TEED, subjects of the Queen of England,residing at London, England, have invented certain new and useful Improvements in or Relating to the EX- traction of Precious Metals from Their Ores, (for which Letters Patent have been granted to us in the following countries, to wit: England, No. 18,592,dated October 1, 1894; Germany, No. 83,292, dated November 13, 1894, and England, Nos. 18,003 and 18,146, dated September 21, 1894, and September 24, 1894, respectively,) of which the following is a specification.

This invention relates to the solution of precious metals generally, but particularly to that of gold and silver, from their ores.

By present known methods or processes where cyanid of potassium is used the time required for perfect extraction by solution is lengthy, and such processes can only be successfully applied in particular cases-such, for example, as the following: The gold must be in a state of very fine division among the other compounds or substances present in the ore, and the substances in the ore (other than precious metals or their compounds) must not be capable of rapidly destroying or deteriorating the solution of cyanid used. Further,the precious-metal contents of the ore must not be relatively great. Thus ores containing coarse gold or a high value of gold per ton, whether coarse or fine, copper compounds, and certain other metalliferous substances cannot be successfully treated by cyanid, and pyritic ores give rise to many difficulties and cyanid losses. Even under the most favorable conditions a great loss of cyanid occurs, owing,among other causes,to the action of the carbonic acid in the air, residual alkali in the prepared ore, the formation of Prussian blue and other compound cyanids, 850. These losses are caused or accentuated by the fact that potassium cyanid alone is incapable of dissolving gold and as at present employed requires oxidation, atmospheric or otherwise, to eifect the production of the soluble double cyanid of potassium and gold and that even with the aid of air the solvent power of cyanid on gold is comparatively feeble and requires a lengthened period to effect complete solution.

Now We have found that halogen compounds of cyanogen-to wit, chlorid, bromid, or iodid of cyanogenwhen added in certain proportions to cyanid of potassium in water form a series of solvents for precious metals, particularly gold, of great power and efficiency. The solution of the precious metal in such alkaline solvents is rapid and complete, and the secondary reactions of the solvent on the other compounds of the ore, such as copper or iron pyrites, are very limited in extent, the shortness of the time required to dissolve the gold of the ore reducing them to a minimum. The solvent reaction which occurs may be represented by the following chemical equation:

It is to be noticed here that no oxygen or oxygenation process is required, but that it is a chemical reaction independent of the oxygen of the air or of the oxygen of the water. It is also to be noticed in this connection that these haloid compounds of cyanogen are of considerable stability and do not act by the liberation of the haloid element; but the whole reaction is complete as between the chemicals employed and the gold-i. e.,without the further intervention of any extraneous agent. The quantity of cyanogen chlorid, bromid, or iodid to produce the solvent reaction named in this process must be accompanied bya proportion of potassium cyanid equivalent to three molecules of the latter to each one molecule of the haloid compounds above mentioned. For example, one molecule of cyanogen chlorid having a molecular weight of 61.5 requires three molecules of potassium cyanid a molecular weight of 3 X 65.5, and in the case of bromid of cyanogen one molecule of this compound having molecular weight of one hundred and six requires three molecules of cyanid of potassium of total molecular weight 196.5, as before. A similar proportion is required for iodid of cyanogen. This is the highest proportion of cyanogen haloid claimed proportionately to potassium cyanid; but a large excess of potassium cyanid is generally preferable.

We may proceed in carrying out our invention in any of the following ways: First, we may form separately chlorid, bromid, or iodid of cyanogen by any known and suitable method and add arequisite proportion of any one or a mixture of such products to the requisite proportion of cyanid of potassium in water. This solution suitably diluted is then applied to the crushed ore or ore products, which may be contained in any suitable tank or vessel, open or closed, constructed of any suitable material, such as wood. The solution of the gold or precious metal is effected in a very short time, and the gold-bearing solution is then drawn off and the precious metal recovered therefrom by any known means. The cyanogen haloid may, if desired, be applied after the cyanid of potassium has been mixed with the ore. Second, we may proceed also by acting upon the solution of potassium cyanid or the solution of any suitable cyanid of the alkalies or alkaline earths by chlorin, bromin, or iodin in quantitysufficient to produce the requisite amount of the desired cyanogen haloid according to the chemical equation 01 KOy KOl CyOl and keeping undecomposed a sufficient excess of cyanid of potassium for the required combined solvent action on the precious metal. The solution thus prepared is then applied in the same manner as specified above.

A further application of our invention relates to the treatment of the waste liquors which are obtained from the process of the extraction of the gold or precious metals from the solvent solution by the action of zinc on.

these latter. The addition of a halogen element or of mixtures capable of yielding the same, such as hydrochloric acid with a solution of permanganate of potash or a solution of bleaching-powder to which the addition of a small quantity of mineral acid is made, decomposes the double cyanid of zinc and potassium which is found therein with the formation of insoluble cyanid of zinc (which may be separated from the liquors by filtration or other means) and effects the regeneration of the haloid cyanogen compound,which can thus be used again for fresh solvent purposes when mixed with a suitable proportion of potassium cyanid. This may be represented by the following chemical equation:

K ZnCy +2Ol :2KCl+ZnGy +2CyCL Although we have herein indicated certain proportions in which the haloid cyanogen compound may be added to the potassium cyanid or other suitable cyanid,we do not bind ourselves to these proportions and may use any mixture of the above substances or compounds in any state of dilution in water, the essence of our invention consisting in the employment of the haloid compounds of cyanogen in combination with free cyanid of potassium or other suitable cyanid of the alkalies or alkaline earths as a solvent for precious metals from their ores, and we may act with such solvents upon ore in any convenient manner, either at the ordinary or at increased or reduced temperatures and pressures and upon greater or less proportions of ore or precious-metal-containing compound.

WVe claim- 1. The process herein described for dissolving precious metals from their ores in solution, the same consisting in combining with a suitable cyanid of the alkalies or alkaline earths, a suitable proportion of a halogen compound of cyanogen and then applying the solution to the crushed ore, as set forth.

2. The process herein described for dissolving precious metals from their ores in solution, the same consisting in combining with a suitable quantity of cyanid of potassium in water, a halogen compound of cyanogen in suitable proportions and then applying the solution to the crushed ore, as set forth.

3. The process herein described for dissolving precious metals from their ores in solution, the same consisting in combining with a suitable quantity of cyanid of potassium in water, a suitable proportion of bromid of cyanogen and then applying the solution to the crushed ore, as set forth.

4. The process herein described for dissolving precious metals from their ores in solution, the same consisting in combining with a suitable cyanid of the alkalies or alkaline earths a small proportion of a halogen so as to form a halogen compound of cyanogen, leaving an excess of cyanid undecomposed, and then applying the solution to the crushed ore.

In testimony whereof we have hereto set our hands in the presence of the two subscribing witnesses.

HENRY LIVINGSTONE SULMAN. FRANK LITHERLAND TEED.

WVitnesses:

GEO. J. B. FRANKLIN, WALTER J. SKERTEN. 

